Terpstra M, Andersen P M, Gruetter R
Center for Magnetic Resonance Research, University of Minnesota, 385 East River Road, Minneapolis, Minnesota 55112, USA.
J Magn Reson. 1998 Mar;131(1):139-43. doi: 10.1006/jmre.1997.1353.
Eddy current effects induced by switched gradients in proximal conducting structures are traditionally reduced by applying preemphasis currents whose amplitudes and decay characteristics must be set to offset the eddy current fields. We present an expeditious, localized, and quantitative method for mapping and adjusting the parameters for eddy current compensation. Mapping is based on analysis of projections as used in the fast automatic shimming technique by mapping along projections (FASTMAP). Adjustment methods are demonstrated in high-field horizontal bore systems. The proposed localized eddy current mapping technique may also be used for localized measurements in situations where asymmetric conducting structures may cause nonlinear eddy current fields, such as in interventional MRI and open magnet designs.
传统上，近端传导结构中开关梯度引起的涡流效应可通过施加预加重电流来降低，预加重电流的幅度和衰减特性必须设置为抵消涡流场。我们提出了一种快速、局部化且定量的方法，用于绘制和调整涡流补偿参数。映射基于沿投影映射（FASTMAP）的快速自动匀场技术中使用的投影分析。在高场水平孔径系统中展示了调整方法。所提出的局部化涡流映射技术也可用于非对称传导结构可能导致非线性涡流场的情况，如介入式磁共振成像和开放式磁体设计中的局部测量。
